The invention relates to substituted pyrimidine compounds and to the use of such compounds. Said compounds have valuable therapeutic properties and can be used in particular to treat disorders which respond to dopamine D3 ligands.
Compounds which are of the type under discussion here and have physiological activity have in some cases been disclosed. Thus, DE 21 39 082 and DE 22 58 561 describe pyrimidine derivatives and pyrimidone derivatives with basic substituents as drugs for lowering blood pressure. These pyrimidine and pyrimidone derivatives have the formulae: 
where in (A) X is, inter alia, sulfur, A is C1-C6-alkylene, and R1, R2, R3 and Z are various substituents. In (B), X and Y are each oxygen or sulfur, A is C2-C6-alkylene and R and Z are various substituents.
Neurons receive their information inter alia via G protein-coupled receptors. There are numerous substances which exert their effect via these receptors. One of them is dopamine.
Confirmed findings on the presence of dopamine and its physiological function as neurotransmitter have been published. Cells which respond to dopamine are connected with the etiology and schizophrenia and Parkinson""s disease. These and other disorders are treated with drugs which interact with dopamine receptors.
By 1990, two subtypes of dopamine receptors had been clearly defined pharmacologically, namely D1 and D2 receptors.
Sokoloff et al., Nature 1990, 347: 146-151, found a third subtype, namely D3 receptors. They are expressed mainly in the limbic system. The D3 receptors differ structurally from the D1 and D2 receptors in about half the amino-acid residues.
The effect of neuroleptics has generally been ascribed to their affinity for D2 receptors. Recent receptor-binding studies have confirmed this. According to these, most dopamine antagonists, like neuroleptics, have high affinity for D2 receptors but only low affinity for D3 receptors.
DE-A 19 46 172 describes heterocyclic ethers of the formula 
where R1 is a mononuclear, unsaturated, nitrogen-containing, heterocyclic ring system which may be substituted by lower alkyl, lower alkoxy, phenylalkyl or phenyl groups, R2 is phenyl which is unsubstituted or substituted by lower alkyl or lower alkoxy groups or chlorine or bromine atoms and which may contain 1 or 2 nitrogen atoms in the ring, and A is a straight-chain or branched alkylene radical with 2 to 6 carbon atoms. These compounds have xcex1-sympathicolytic activity and accordingly have a sedative, hypotensive and vasodilating effect.
We have now found, surprisingly, that certain pyrimidine compounds have a high affinity for the dopamine D3 receptor and a low affinity for the D2 receptor. They are thus selective D3 ligands.
The present invention therefore relates to the use of pyrimidine compounds of the general formula I: 
where
A is C1-C18-alkylene which may comprise at least one group selected from O, S, NR4, CONR4, NR4CO, COO, OCO and a double or triple bond,
B is 
R1, R2, R3 are selected, independently of one another, from among H, halogen, OR4, NR4R5, SR4, CF3, CN, CO2R4 and C1-C8-alkyl which is unsubstituted or substituted by OH, OC1-C8-alkyl or halogen,
R4 is H, C1-C8-alkyl which is unsubstituted or substituted by OH, OC1-C8-alkyl or halogen,
R5 has the meanings indicated for R4 or is COR4 or CO2R4;
Ar is phenyl, pyridyl, pyrimidyl or triazinyl, where Ar may have from one to four substituents which are selected, independently of one another, from OR5, C1-C8-alkyl, C2-C6-alkenyl, C2-C6-alkynyl, halogen, CN, CO2R4, NO2, SO2R4, SO3R4, NR4R5, SO2NR4R5, SR4, CF3, CHF2, a 5- or 6-membered carbocyclic aromatic or non-aromatic ring and a 5- or 6-membered heterocyclic aromatic or non-aromatic ring having 1 to 3 hetero atoms which are selected from O, S and N, where the ring may be unsubstituted or substituted by C1-C8-alkyl, Hal, OC1-C8-alkyl, OH, NO2, CF3, and where Ar may also be fused to a carbocyclic or heterocyclic ring of the type defined above,
xe2x80x83and the salts thereof with physiologically tolerated acids for producing a pharmaceutical composition for treating disorders which respond to dopamine D3 receptor antagonists or agonists.
The invention also relates to the pyrimidine compounds of the formula Ixe2x80x2
where
A, B, Ar, R1, R2 and R3 have the meanings stated in claims 1 to 8, and the salts thereof with physiologically tolerated acids, excepting the compounds of the formula 
wherein R1 is OH or SH, R2 and R3 are, independently one of another, H, C1-C6-alkyl, OC1-C6-alkyl, SC1-C6-alkyl, CO2H, OH, SH, NR4R5 or halogen, where R4 and R5 are H or C1-C6-alkyl, A is SC1-C6-alkylene, NHC1-C6-alkylene or N(C1-C6-alkyl)-C1-C6-alkylene, B is 
and Ar is phenyl which may have one or more substituents selected from C1-C4-alkyl, OC1-C4-alkyl, SC1-C4-alkyl, NO2, CF3, F, Cl or Br.
The compounds used according to the invention are selective dopamine D3 receptor ligands which intervene regioselectively in the limbic system and, because of their low affinity for the D2 receptor, have fewer side effects than classical neuroleptics, which are D2 receptor antagonists. The compounds can therefore be used to treat disorders which respond to dopamine D3 receptor antagonists or agonists, eg. for treating disorders of the central nervous system, in particularly schizophrenia, depression, neuroses and psychoses. They can additionally be used to treat sleep disorders and nausea and as antihistamines.
Within the scope of the present invention, the following terms have the meanings indicated below: alkyl (also in radicals such as alkoxy, alkylamino, etc.) means a straight-chain or branched alkyl group having 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms and, in particular, 1 to 4 carbon atoms. The alkyl group can have one or more substituents which are selected, independently of one another, from OH and OC1-C8-alkyl.
Examples of an alkyl group are methyl, ethyl, n-propyl, i-propyl, n-butyl, isobutyl, t-butyl, etc.
Alkylene stands for straight-chain or branched radicals having, preferably, 2 to 15 carbon atoms, particularly preferably3 to 10 carbon atoms.
The alkylene groups may comprise at least one of the abovementioned groups. This canxe2x80x94just like the double or triple bond mentionedxe2x80x94be arranged in the alkylene chain at any point or at the end of the chain so that it connects the chain to the pyrimidine residue. The latter is preferred. When the alkylene group comprises a double or triple bond, it has at least three carbon atoms in the chain.
Halogen is F, Cl, Br, I and, in particular, Cl, Br, I.
R1, R2 and R3 are preferably, independently of one another, H, C1-C8-alkyl, NR4R5, SR4 or OR4, where R4 and R5 are, independently of one another, H or C1-C8-alkyl.
Ar preferably has one or two substitutents which are selected, independently of one another, from OR5, C1-C8-alkyl, Hal, CN, CO2R4, NO2, SO2R4, SO3R4, NR4R5, SO2NR4R5, SR4, CF3, CHF2, a 5- or 6-membered carbocyclic, aromatic or non-aromatic ring and a 5- to 6-membered heterocyclic, aromatic or non-aromatic ring having 1 to 3 hetero atoms which are selected from O, S and N, where the ring may be unsubstituted or substituted by C1-C8-alkyl, Hal, OC1-C8-alkyl, OH, NO2, CF3 and where Ar may also be fused to a carbocyclic or heterocyclic ring of the type defined above.
If Ar has one or two substituents, these are preferably in the m position.
They are preferably selected independently from halogen, CF3, CHF2, CN, NO2, OR4, NR4R5, C1-C8-alkyl, OC1-C8-alkyl, phenyl and SR4, where R4 and R5 are H or C1-C8-alkyl. If one of the substituents is C1-C8-alkyl, a branched group and, in particular, isopropyl or t-butyl is preferred.
Ar preferably has at least one substituent and is, in particular, 
where D1, D2 and D3 are, independently of one another, CR or N, and R, X and Y are H or have the meanings indicated above or below.
Ar is preferably unsubstituted or substituted phenyl, 2-, 3- or 4-pyridinyl or 2-, (4(6)- or 5-pyrimidinyl.
When one of the substituents of the radical Ar is a 5- or 6-membered heterocyclic ring, examples thereof are a pyrrolidine, piperidine, morpholine, piperazine, pyridine, 1,4-dihydropyridine, pyrimidine, triazine, pyrrole, thiophene, thiazole, imidazole, oxazole, isoxazole, pyrazole or thiadiazole residue.
When one of the substituents of the radical Ar is a carbocyclic radical, it is, in particular, a phenyl, cyclopentyl or cyclohexyl radical.
When Ar is fused to a carbocyclic or heterocyclic radical, it is, in particular, a naphthalene, di- or tetrahydronaphthalene, quinoline, di- or tetrahydroquinoline, indole, dihydroindole, benzimidazole, benzothiazole, benzothiadiazole, benzopyrrole or benzotriazole residue.
A preferred embodiment is the use of compounds of the formula I where A is C1-C10-alkylene which may comprise at least one group selected from O, S, NR4, cyclohexylene and a double or triple bond. Particularly preferred compounds of the formula I are those where A is C3-C10-alkylene which may comprise at least one group selected from O, S, NR4 and a double or triple bond.
Another preferred embodiment comprises use of the compounds of the formula I where R1, R2 and R3 are, independently of one another, H, C1-C8-alkyl which can be unsubstituted or substituted by OH, OC1-C8-alkyl or halogen, or OH, OC1-C8-alkyl, SR4 or NR4R5, where R4 and R5 are, independently of one another, H or C1-C8-alkyl;
Ar is phenyl, pyridyl or pyrimidyl which may have one, two, three or four substituents selected from H, C1-C8-alkyl which may be substituted by OH, OC1-C8-alkyl or halogen, or OR4 where R4 is H, C1-C8-alkyl which may be substituted by OH, OC1-C8-alkyl or halogen, or CHF2, CF3, CN, halogen, C2-C6-alkenyl, C2-C6-alkynyl, C5-C6-cycloalkyl, phenyl, naphthyl and a 5- or 6-membered heterocyclic aromatic radical with 1 to 3 hetero atoms selected from O, N and S.
Another preferred embodiment comprises use of the compounds of the formula I where B is 
Another preferred embodiment is the use of the compounds of the formula I where Ar is phenyl which has one to four substituents which are selected, independently of one another, from H, C1-C8-alkyl which may be substituted by OH, OC1-C8-alkyl or halogen, or phenyl, naphthyl, pyrrolyl, CN NO2, CF3, CHF2, halogen, SO2R4 or SR4 where R4 is H or C1-C8-alkyl, or where the substituents are selected, independently of one another, from C1-C8-alkyl, phenyl, CF3, CHF2, CN, NO2, halogen, OC1-C8-alkyl or SR4 where R4 is H or C1-C8-alkyl.
Another preferred embodiment is the use of compounds of the formula I where R1 is H, C1-C8-alkyl which is unsubstituted or substituted by OH, OC1-C8-alkyl or halogen, or OR4, SR4 or NR4R5 where R4 and R5 are, independently of one another, H or C1-C8-alkyl; R2 is H, OR4 or C1-C8-alkyl; and R3 is H.
Another preferred embodiment is the use of compounds of the formula I where Ar is pyrimidinyl which has one to three substituents which are selected, independently of one another, from H, C1-C8-alkyl, phenyl, naphthyl, C5-C6-cycloalkyl, OH, OC1-C8-alkyl, halogen, CN, NO2, CF3, CHF2 and a 5- or 6-membered heterocyclic aromatic or non-aromatic radical with 1 to 3 hetero atoms selected from O, N and S.
Another preferred embodiment is the use of compounds of the formula I where Ar is pyridinyl which has one to four substituents which are selected, independently of one another, from H, C1-C8-alkyl, phenyl, naphthyl, OH, OC1-C8-alkyl, halogen, CF3, CN, C2-C6-alkenyl, C2-C6-alkynyl and a 5- or 6-membered heterocyclic aromatic radical with 1 to 3 hetero atoms selected from O, N and S.
The invention also embraces the acid addition salts of the compounds of the formula I with physiologically tolerated acids. Examples of suitable physiologically tolerated organic and inorganic acids are hydrochloric acid, hydrobromic acid, phosphoric acid, sulfuric acid, oxalic acid, maleic acid, fumaric acid, lactic acid, tartaric acid, adipic acid or benzoic acid. Other acids which can be used are described in Fortschritte der Arzneimittelforschung, Volume 10, pages 224 et seq., Birkhxc3xa4user Verlag, Basle and Stuttgart, 1966.
The compounds of the formula I may have one or more centers of asymmetry. The invention therefore includes not only the racemates but also the relevant enantiomers and diastereomers. The invention also includes the tautomeric forms in each case.
The compounds of the formula Ixe2x80x2 can be prepared by methods similar to conventional ones as described, for example, in A. R. Katritzky, C. W. Rees (ed.), xe2x80x9cComprehensive Heterocyclic Chemistryxe2x80x9d, 1st Edition, Pergammon Press 1984, in particular Vol. 3, Part 2A; D. J. Brown xe2x80x9cThe Pyrimidinesxe2x80x9d, in xe2x80x9cThe Chemistry of Heterocyclic Compoundsxe2x80x9d, E. C. Taylor (ed.), John Wiley and Sons Inc. NY, in particular Vol. 16+Suppl. I+II (1985) and Vol 52 (1994) and literature cited therein. The process for preparing the compounds comprises
i) reacting a compound of the general formula II: 
xe2x80x83where Y1 is a conventional leaving group, with a compound of the general formula III
Hxe2x80x94Bxe2x80x94Ar;
ii) to prepare a compound of the formula Ixe2x80x2 where A is oxygen or sulfur or NR4:
xe2x80x83reacting a compound of the general formula IV: 
xe2x80x83where Z1 is O, S or NR4, and A1 is C0-C18-alkylene, with a compound of the general formula VI
Y1xe2x80x94A2xe2x80x94Bxe2x80x94Ar
xe2x80x83where Y1 has the abovementioned meanings, and A2 is C1xe2x80x94C18-alkylene, where A1 and A2 together have 1 to 18 carbon atoms,
iii) to prepare a compound of the formula Ixe2x80x2 where A comprises the group COO or CONR4:
xe2x80x83reacting a compound of the general formula VII: 
xe2x80x83or a salt thereof, where Y2 is OH, OC1-C4-alkyl, Cl or, together with CO, is an activated ester group, and A1 has the abovementioned meanings, with a compound of the formula VIII:
Z1xe2x80x94A2xe2x80x94Bxe2x80x94Ar
xe2x80x83where A2 has the abovementioned meanings, and Z1 is OH or NHR4,
iv) to prepare a compound of the formula Ixe2x80x2 where A comprises the group OCO or NR4CO:
xe2x80x83reacting a compound of the formula IV 
xe2x80x83where Z1 is O or NR4, with a compound of the formula X:
Y2COxe2x80x94A2xe2x80x94Bxe2x80x94Ar
xe2x80x83where A2, B and Y2 have the abovementioned meanings, and where R1, R2, R3, A, B and Ar have the above-mentioned meanings.
The reactions described above generally take place in a solvent at from room temperature to the boiling point of the solvent used. Examples of solvents which can be used are ethyl acetate, tetrahydrofuran, dimethylformamide, dimethoxyethane, toluene, xylene or a ketone, such as acetone or methyl ethyl ketone.
An acid acceptor is present if required. Suitable acid acceptors are inorganic bases such as sodium or potassium carbonate, sodium methoxide, sodium ethoxide, sodium hydride or organic bases such as triethylamine or pyridine. The latter can also serve as solvents.
The crude product is isolated in a conventional way, for example by filtration, removal of the solvent by distillation or extraction from the reaction mixture, etc. The resulting compound can be purified in a conventional way, for example by recrystallization from a solvent, chromatography or conversion into an acid addition compound.
The acid addition salts are prepared in a conventional way by mixing the free base with the appropriate acid, possibly in solution in an organic solvent, for example a lower alcohol such a methanol, ethanol or propanol, an ether such as methyl t-butyl ether, a ketone such as acetone or methyl ethyl ketone, or an ester such as ethyl acetate.
The abovementioned starting materials are disclosed in the literature or can be prepared by known processes.
To treat the abovementioned disorders, the compounds according to the invention are administered in a conventional manner orally or parenterally (subcutaneously, intravenously, intramuscularly, intrapertioneally). Administration can also take place with vapors or sprays through the nasopharyngeal space.
The dosage depends on the age, condition and weight of the patient and on the mode of administration. As a rule, the daily dose of active substance is about 10 to 1000 mg per patient and day on oral administration and about 1 to 500 mg per patient and day on parenteral administration.
The invention also relates to pharmaceutical compositions which contain the compounds according to the invention. These compositions are in the usual solid or liquid pharmaceutical administration forms, for example as tablets, film-coated tablets, capsules, powders, granules, sugar-coated tablets, suppositories, solutions or sprays. The active substances can in these cases be processed with conventional pharmaceutical aids such as tablet binders, fillers, preservatives, tablet disintegrants, flow regulators, plasticizers, wetting agents, dispersants, emulsifiers, solvents, release-slowing agents, antioxidants and/or propellant gases (cf. H. Sucker et al., Pharmazeutische Technologie, Thieme-Verlag, Stuttgart, 1978). The administration forms obtained in this way normally contain the active substance in an amount of from 1 to 99% by weight.